Update dependency sass-loader to v15

| datasource | package     | from   | to     |
| ---------- | ----------- | ------ | ------ |
| npm        | sass-loader | 13.3.3 | 15.0.0 |


Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -16,7 +16,7 @@
     "devDependencies": {
         "laravel-mix": "6.0.49",
         "sass": "1.100.0",
-        "sass-loader": "13.3.3",
+        "sass-loader": "15.0.0",
         "vue-loader": "16.8.3"
     },
     "dependencies": {